A source-side node is a communication node used by a terminal in a communication. The source-side node may be, for example, a source-side core network node or a source-side access network node.
A target-side node is a communication node used by the terminal in the communication after a handover. The target-side node may be, for example, a target-side core network node or a target-side access network node.
The terminal may usually encounter a problem of handover between communication nodes in the communication. Mainly, an access network node and a core network node are involved in the handover between the communication nodes. If only the access network nodes are involved in the handover between the communication nodes, the handover may be performed between the access network nodes through an X2 interface. The handover between the communication nodes is very complicated if the core network node are involved in the handover. An S1 interface handover may be executed in the handover, once a Mobility Management Entity (MME) alters. A handover procedure starts from a source-side evolved Node B (ENB) and arrives at a target-side MME via a source-side MME. Then, the target-side MME interacts with a target-side ENB and forwards related information to the source-side ENB via the source-side MME, to complete the handover procedure. Multiple times of interactions between MME and ENB are involved in the procedure and the signaling procedure is complicated. Network congestion may be easily caused if many UEs initiate similar handovers. An inter-RAT handover (a handover between GSM EDGE Radio Access Network/Universal Terrestrial Radio Access Network (GERAN/UTRAN) and Evolved Universal Terrestrial Radio Access Network (EUTRAN)) is similar to the above (in the inter-RAT handover, Serving GPRS Support Node (SGSN) provides a service for the GERAN/UTRAN and MME provides a service for the EUTRAN, which is equivalent to the case that CN node alters). Multiple times of interactions between CN and RAN are involved in the handover, which also increases the signalling burden of the network and causes a waste of the network resource.